Zack's Kernel News

Zedtrace Tracepoint Filter

Tom Zanussi posted his own kernel tracing tool, zedtrace, with a minimal home page at: http://utt.sourceforge.net/zedtrace.html. It lets the user trace any tracepoints already defined in the kernel binary. Sophisticated filtering is provided by the Perl language. Python and Ruby support, he said, was on the way. Christoph Hellwig said he liked Tom's tool but felt that tracepoints themselves were badly in need of revision. He acknowledged this wasn't zedtrace's fault.

Status of exofs

Boaz Harrosh submitted an update to the exofs filesystem. Exofs is designed for Object Storage Devices (OSDs), a relatively new type of storage device that takes object orientation into the drive itself. Instead of dealing with a character stream or with blocks of related data, OSDs present data as a collection of objects, that in turn may be composed of other objects. The idea is that this higher level view into data allows the user more control over managing the data and providing security.

The new version is substantially updated. It replaces the kernel-based mkexofs tool with a userspace library that exports the same API. It also incorporates fixes that have gone into ext2 in the recent past. Because exofs is a fork of the ext2 code base, any fix to ext2 is likely to be a fix to exofs as well. Boaz also modified the API used to perform object access. Exofs exports a standard block-oriented interface, so that exofs filesystems can be treated the same as any other block-based filesystem; it also provides an additional API to support OSD calls. The previous version used an API from IBM that was different from the standard OSD API. The new version uses the open-osd API directly.

VMUFAT Filesystem for the Dreamcast

Adrian McMenamin explained that the Sega Dreamcast visual memory unit implemented a filesystem similar to FAT16. He posted a driver for the VMUFAT filesystem (culled from an earlier attempt by him long ago) and said he intended to document the entire filesystem and write a userspace tool to create a VMUFAT image. He also pointed out in the KConfig description that this filesystem was really very specialized for the Dreamcast and would not make a great choice on other drives. A bunch of folks offered feedback, mainly pointing out a few legacy bugs left over from Adrian's earlier code. By the end of it, Adrian decided to do a more thorough rewrite and aim for inclusion in a later kernel.

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